Global Positioning Systems (GPS's) are widely used in vehicle systems. Agricultural tractors use GPS's, for example, to implement automatic steering through pre-defined routes within agricultural fields.
Performance of automatic steering systems may be degraded for so-called retrofit systems that effectively bolt on to existing vehicles. Vehicle configurations and soil type and conditions may also degrade automatic steering performance. A vehicle lateral dynamics model identification can be derived based on vehicle parameter estimations, and this model can be used to develop a steering controller that may overcome some above the aforementioned degradations of performance. However, vehicle parameters are hard to measure and are not always accessible. A sinusoidal sweep method may also be used for open-loop vehicle lateral dynamics model identification. With this method, a set of sinusoidal tests within a range of frequencies are analyzed to determine the system's frequency response. This open loop sinusoidal sweep approach may not be ideal in agricultural settings due to the limited area available to perform the necessary tests. Closed loop identification is considered more appropriate for farm vehicle identification.